Constant velocity joints (CV joints) are common components in vehicles. Constant velocity joints are often employed where transmission of a constant velocity rotary motion is desired or required. CV joints are typically greased or otherwise lubricated for the life of the component. The joints are sealed to retain the grease or lubricant inside the joint while keeping contaminants and foreign matter, such as water and dirt, out of the joint. Moreover, a sealing boot, which may be made of rubber, thermoplastic, silicone material, or the like, usually encloses annular portions at an axial end of the CV joints with a shaft interposed therethrough. The opposing axial end may also be enclosed with a grease cover to seal the CV joint from the contaminants.
During operation, a CV joint may create excess internal pressures in the inner chamber of the joint. In such instances, it is often desirable to vent pressurized gases from the chamber of the joint to the outer atmosphere to reduce the internal temperature of the joint. This function can prevent undesirable pressure build-up during operation of the joint that could damage or compromise components such as the sealing boot. Consequently, many CV joints include techniques for venting. Examples of a known venting techniques include a small hole in the center of the grease cap. However, this venting technique may allow an unwanted release of the grease or lubricant.
FIG. 1 illustrates a CV joint 20 having a central axis A-A. CV joint 20 includes driven end 22 and a driving end 24. CV joint 20 further includes a joint assembly 26 coupled to a shaft 28 with a boot cover assembly 30 connected therebetween. CV joint 20 further includes a grease cover 32 that seals the driving end 24. Boot cover assembly 30 includes a metal cover 34 and a flexible boot 36. A portion of metal cover 34 is crimped onto boot 36 for attachment thereto. Boot cover assembly 30 and grease cover 32 protect the moving parts of CV joint 20 during operation by retaining the grease or lubricant inside the joint while keeping contaminants and foreign matter, such as water and dirt, out of the joint assembly 26.
The grease cover 32 may include a vent valve aperture to accommodate a vent valve (not shown). The joint assembly 26 includes a cage 40, a first rotational member or outer race 42, a second rotational member or inner race 44, and a plurality of balls (not shown). The cage 40 retains the balls between the first rotational member 42 and the second rotational member 44 in a generally equally spaced circumferential orientation. The shaft 28 is splined to second rotational member 44 to transmit torque.
Collectively, at least the shaft 28, boot cover assembly 30, first rotational member 42, and the grease cover 32 form a joint chamber 48. Joint chamber 48 contains grease or other lubricant (not shown) for lubrication between cage 40, first rotational member 42, second rotational member 44, and the balls.
The grease cover 32 has a generally circular body 50 defined, at least in part, by a peripheral edge 52 and a generally annular sealing surface 58, as best seen in FIGS. 1A and 2. The first rotational member 42 has a grease cover end 60 having a generally cylindrical inner surface 62 and a generally annular mating surface 64. A gasket 70 is interposed between the sealing surface 58 of the grease cover 32 and the mating surface 64 of the first rotational member 42.
During vehicle operation, CV joints 20 are typically heated due to the rotation and resulting friction between moving parts. After vehicle operation, the pressure within the joint chamber 48 typically increases due to the heat, and the lubricants are typically softened and have a lower viscosity due to the heat. The grease cover 32 is therefore required to seal the joint chamber 48 at varying operational temperatures and pressures.
Typically, the grease cover 32 is press fit into the first rotational member 42 by providing an interference fit between the inner surface 62 and the peripheral edge 52. Thus, the force required to press fit the grease cover 32 into the inner surface 62 defines the compressive force on the gasket 70. However, the expansion force generated by the gasket 70 acts against the retention of the grease cover 32 with the first rotational member 42. What is needed, therefore, is a method and apparatus for sealing a grease cover with a CV joint. A favorable method would result in a predictable amount of sealing force on a gasket, such as the gasket 70.